Drugs To Stop Diarrhea (Anti-Diarrheal Medication)

In most instances diarrhea is an acute symptom that often resolves on its own without treatment. Apart from requiring oral rehydration to maintain an adequate intake of fluid and electrolytes to counteract the loss in diarrheal stool, additional treatment for diarrhea is not necessary. However, these are times when diarrhea itself needs to be treated. In this case anti-diarrheal treatment involves using drugs that will stop the diarrhea itself irrespective of whether the underlying cause of the diarrhea has been treated or not. It is more often considered for severe, persistent or chronic diarrhea rather than acute diarrhea.

What is an antidiarrheal?

An antidiarrheal is a drug that treats diarrhea, either by stopping it or reducing the frequency of diarrheal stools. Since diarrhea is a symptom, it is always advisable to treat the root cause. However, sometimes diarrhea itself has to be treated. Antidiarrheal drugs are available as either over-the-counter (OTC) medication or prescription medications. Some drugs indicated for other conditions like certain painkillers may also stop diarrhea, however, an antidiarrheal drug is specifically indicated for relieving diarrhea.

Types of Antidiarrheals

There are six types of drugs used for treating diarrhea. Two types, opioids and stool bulking agents, may be used for all types of diarrhea irrespective of the cause. The other types are used for specific conditions where diarrhea is present.


Opioids are the most commonly used antidiarrheals. It can be used for most forms of diarrhea. These drugs include:

  • Diphenoxylate
  • Loperamide

Most people worry about opioids being addictive since these are known to be the group of strong painkillers (narcotics) which cause euphoria. However, the opioid antidiarrheal drugs are usually not an addiction risk. Diphenoxylate does not relieve pain at standard doses, and atropine is added to it to prevent overuse due to central nervous system effects at higher doses. Loperamide does not cross the blood-brain barrier, has no pain-relieving properties and is not addictive.

These drugs act on the opioid receptors in the intestine thereby inhibiting water excretion into the bowels. This makes the stool less fluid and essentially promotes constipations. It also indirectly increases water absorption from the bowels, and blocks the nerves that increase bowel motility. Despite its effectiveness, opioids may not be desirable to treat diarrhea. In the cases of infectious diarrhea, opioids may prevent the expulsion of microbes and toxins that are causing the diarrhea.

Bulking Agents

Bulking agents can also safely be used for treating diarrhea. However, it is not usually as effective as opioids and may only help reduce watery diarrhea in some instances.

  • Psyllium
  • Methylcellulose

Although bulking agents are more often prescribed for constipation it does not mean that it will not help in some cases of diarrhea. These substances are not laxatives and will not worsen diarrhea. It acts by absorbing water in the bowels, thereby making stool more firm. It may be a better choice for chronic diarrhea particularly in functional bowel disorders like irritable bowel syndrome (IBS), where it can be used daily.

Other Drugs

The following drugs can also be used to treat diarrhea but only when diarrhea is caused by specific conditions.

  • Absorbents for infectious diarrhea work by absorbing the toxins produced by infectious agents. Examples: kaolin, pectin and methylcellulose.
  • Bile acid binding resins form a complex with bile salts to reduce water secretion into the bowels. Examples: cholestyramine.
  • Octerotride that mimics the digestive hormone somastatin and inhibits bowel motility.
  • Bismuth subsalicylate has antimicrobial activity, binds enterotoxins, regulates the water balance in the bowels and reduces inflammation. It may be used for traveler’s diarrhea.

Side Effects

The side effects of antidiarrheal drugs will focus on opioids since these are the most commonly used OTC medication for treating diarrhea. These side effects are undesirable symptoms that arise with the use of a drug. With opioid antidiarrheals the side effects may include:

  • Abdominal pain
  • Nausea and sometimes vomiting
  • Constipation
  • Dizziness

Less commonly loperamide may cause:

  • Dry mouth
  • Fatigue
  • Angioedemia
  • Skin rashes

Opioid antidiarrheal drugs can also cause toxic megacolon if used in conditions like severe ulcerative colitis, one of the two types of inflammatory bowel disease. Diphenoxylate can lead to physical dependence if used in large doses and cause euphoria.


Sometimes the use of a drug is not advisable as it may lead to side effects and compromise the health of a person. This is known as contraindications. With opioid antidiarrheals and specifically loperamide, its contraindicated in the following instances:

  • Children under 2 years of age unless it is prescribed a doctor. Loperamide should also be used with caution in older children and advice should first be sought from a doctor or pharmacist.
  • Bloody diarrhea or black tarry stools which indicate gastrointestinal bleeding.
  • Any allergic reaction after using the drug.
  • Fever or other signs of an infection unless the drug is prescribed by a doctor.

It is also important to note that loperamide can affect the action of other drugs or have adverse drug interactions when used together with certain medication, like antibiotics, antiretrovirals (HIV/AIDS) and prescription analgesics (painkillers). It is important to seek professional advice from a doctor or pharmacist in these instances.

Dose and Directions of Use

Always follow the directions on the instruction leaflet or packaging of the medication if a pharmacist or doctor has not provided specific instructions. For loperamide, the dosage should be 4mg after the first loose stool and 2mg following each loose stool thereafter. Usually a person should not exceed 8mg/day collectively unless otherwise advised by a doctor or pharmacist. Loperamide should be discontinued in acute diarrhea if there is no improvement after 48 hours of use.

When to see a doctor?

It is always advisable to consult with a doctor when symptoms like diarrhea arise. However, most of us attempt to manage it on our own for the first day or two. Antidiarrheal drugs should not be the first option for treating acute diarrhea. Instead bed rest, sufficient nutrition and oral rehydrating solutions should be the main approach. If the diarrhea is worsening, there are signs of bleeding from the bowels and/or signs of dehydration then immediate medical attention is necessary. Other symptoms that are severe and/or intensifying may also prompt the need for medical attention even if the diarrhea is mild or improving.




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